The ōdachi, also known as nodachi, is a type of Japanese sword characterized by its long blade. It is significantly longer than the standard katana and was primarily used by warriors in specific historical periods. Here's how the ōdachi was typically used:

1. Battlefield Weapon: The ōdachi was primarily employed as a battlefield weapon during specific periods in Japanese history, such as the Kamakura and Muromachi periods (12th to 16th centuries). Its long blade and extended reach made it effective in open-field battles and against multiple opponents.
2. Two-Handed Grip: Due to its size and weight, the ōdachi was typically wielded with a two-handed grip. The warrior held the hilt with both hands, allowing for better control, stability, and power in swinging and striking actions.
3. Slashing Techniques: The ōdachi's design and length allowed for powerful slashing techniques. Warriors could deliver devastating cuts and strikes against both infantry and cavalry. The long blade could reach distant targets, providing an advantage in combat.
4. Formation Breaking: The ōdachi was especially effective in breaking enemy formations due to its extended reach and cutting power. A skilled ōdachi wielder could disrupt tightly packed enemy ranks, creating openings for their allies to exploit.
5. Symbol of Prestige: The ōdachi was also used as a symbol of prestige and status by high-ranking samurai and clan leaders. Carrying an ōdachi demonstrated authority, wealth, and martial prowess.

It's important to note that the ōdachi's use declined with changes in warfare, as battles shifted to more confined spaces and the need for more maneuverable weapons increased. The ōdachi is now primarily considered a ceremonial or display piece, revered for its historical significance and grandeur.